Generally, a vehicle underbody includes a front floor disposed at a front of the vehicle and a rear floor disposed at a back of the vehicle. The rear floor arrangement structure of the vehicle may configure a lower portion of a trunk area of the vehicle. In particular the floor arrangement (e.g., the floor structure) may be configured to support a spare tire accommodated in the trunk area, various other articles, or the like. In the case of eco-friendly vehicles such as an electric vehicle and a hybrid vehicle, a battery, a fuel tank, or the like may also be disposed to be adjacent to the rear floor.
Meanwhile, the existing rear floor of the related art includes various reinforcement structures to effectively cope with a rear collision. However, the the reinforcement structure may be complex. Further, the existing rear floor does not have a technical means for improving the problem of aerodynamic efficiency, a transmission sound, or the like of a vehicle.